Per-airframe settings.
Most likely you didn’t transition the packs off the APU and onto engine bleed. Suggest using the virtual first officer and checklists to do this for you.
It’s required because TO becomes unavailable at a set altitude. No N1 thrust limit set means no ATS. Transition the packs and you’ll be able to select CLB. It’s all in the checklists, and spelled out in the documentation, in sim and in the aircraft directory.